diff --git a/storage/cloud.py b/storage/cloud.py
index 3c28480dc..dd8cd2256 100644
--- a/storage/cloud.py
+++ b/storage/cloud.py
@@ -342,8 +342,8 @@ class _CloudStorage(BaseStorageV2):
           abs_chunk_path = self._init_path(chunk.path)
           part_num = chunk_offset + 1
           chunk_end_offset_inclusive = chunk.length - 1
-          mpu.copy_part_from_key(self.get_cloud_bucket().name, abs_chunk_path, part_num, 0,
-                                 chunk_end_offset_inclusive)
+          mpu.copy_part_from_key(self.get_cloud_bucket().name, abs_chunk_path, part_num,
+                                 start=0, end=chunk_end_offset_inclusive)
         mpu.complete_upload()
 
       except IOError as ioe:
@@ -354,10 +354,9 @@ class _CloudStorage(BaseStorageV2):
         raise ioe
 
     else:
-      logger.warning('Performing client side assmebly of multi-part upload for: %s', final_path)
-
       # We are going to turn all of the server side objects into a single file-like stream, and
       # pass that to stream_write to chunk and upload the final object.
+      logger.warning('Performing client side assmebly of multi-part upload for: %s', final_path)
       concatenated = filelike.FilelikeStreamConcat(self._chunk_generator(chunk_list))
       self.stream_write(final_path, concatenated)
 
@@ -472,3 +471,19 @@ class RadosGWStorage(_CloudStorage):
       return None
 
     return super(RadosGWStorage, self).get_direct_upload_url(path, mime_type, requires_cors)
+
+  def complete_chunked_upload(self, uuid, final_path, storage_metadata):
+    self._initialize_cloud_conn()
+
+    # RadosGW does not support multipart copying from keys, so are forced to join
+    # it all locally and then reupload.
+    # See https://github.com/ceph/ceph/pull/5139
+    chunk_list = self._chunk_list_from_metadata(storage_metadata)
+    if len(chunk_list) == 1:
+      # If there's only one chunk, just "move" the key and call it a day.
+      chunk_path = chunk_list[0].path
+      self._cloud_bucket.copy_key(final_path, self._bucket_name, chunk_path)
+      self._cloud_bucket.delete_key(chunk_path)
+      return
+    concatenated = filelike.FilelikeStreamConcat(self._chunk_generator(chunk_list))
+    self.stream_write(final_path, concatenated)